OBJECTIVE: The objective of this project is to investigate hypotheses related to nutrition and cancer and to cancer chemoprevention. BACKGROUND: The NHEFS is a prospective cohort study created through a systematic followup of persons examined in the NHANES I. NHANES I investigated the health and nutritional status of the United States population and was particularly targeted toward those population groups hypothesized to be at greatest risk of poor health and nutritional deficiency. The survey was carried out on a probability sample of the civilian non-institutional population of the United States from 1971-75. NHANES I included a sociodemographic and medical history, a standardized medical examination, a dietary questionnaire (24-hour recall, with a crude 18-question food requency questionnaire), hematologic and biochemical tests, and anthropometry. METHODS: 14,407 men and women aged 25-74 were eligible for inclusion in the NHEFS cohort. Subjects were first traced and interviewed again for the NHEFS in 1981-84, with additional followups conducted in 1986, 1987, and 1992. Over 1,800 confirmed cancers have been identified through the 1992 followup. PROGRESS: Increased dietary diversity was associated with reduced mortality, including cancer mortality. Increased intake of dietary vitamin C appears to be protective for lung cancer, but dietary carotenoids and vitamin E appear to be protective only in smokers, particularly those with lowest number of pack-years of exposures. Ongoing analyses are evaluating the relations of aspirin use to cancer and bone mineral density to breast cancer.